1. Field of the Invention
The invention relates to a method and apparatus for efficiently extracting heat and mechanical energy from a pressured gas by expanding same in an oscillatable fluid pressure chamber containing a free piston.
2. Description of the Prior Art
In the co-pending application of EDWIN WALTER DIBRELL, Ser. No. 436,852, filed Oct. 25, 1982 now abandoned, and assigned to the Assignee of this application, there is disclosed a form of centrifugal piston expander. Such expander comprises a rotating body upon which an S-shaped cylinder is mounted for co-rotation. A motor initiates such rotation. The S-shaped cylinder defines an S-shaped fluid pressure chamber, extending in a curve from one periphery of the rotating body inwardly through or proximate to the axis of rotation, and then extending outwardly by a reverse curve to a diametrically opposed outer portion of the rotating body. A free piston, having either a ball or oval shaped configuration is slidably and sealably mounted within the S-shaped fluid pressure chamber. Inlet and exhaust valves are provided on each of the two ends of the S-shaped cylinder. Centrifugal force will position the free piston in one of the outer ends of the S-shaped fluid pressure chamber.
The application of a charge of pressured gas through the inlet valve closest to the free piston will cause the piston to move inwardly along the S-shaped fluid pressure chamber and effect the exhaust of any gas remaining in the chamber on the forward side of the piston through the opened exhaust valve at the opposite end of the S-shaped fluid pressure chamber. The inlet valve is closed after the desired charge of pressured gas is introduced into the S-shaped fluid pressure chamber, and the piston continues its travel toward the end of the diametrically opposite end of such chamber, aided by centrifugal force after it passes the axis of rotation. As it approaches such opposite end, the exhaust valve is closed, and a cushion of gas is thus provided to arrest the movement of the piston adjacent the opposite extreme end of the S-shaped fluid pressure chamber. The pressure created in the remaining gas initiates the return movement of the piston and, concurrently or subsequently, the inlet valve adjacent to the piston can be opened to add a charge of gas to the fluid pressure chamber to move the piston along its return path to repeat the cycle.
It was anticipated that the reaction forces on the end walls of the S-shaped fluid pressure chamber produced both by the initial charge of gas and also by the pressure build-up of the trapped pocket of gas used to arrest the movement of the piston would produce a very significant torque aiding in the rotation of the rotatable body and thus permit the device to function as a source of rotating power.
There are, however, a myriad of variables to be considered. The overall diameter of the S-shaped fluid chamber, the internal diameter of the S-shaped fluid chamber, the internal diameter of the S-shaped fluid chamber, the length of the path of the piston, the curvature of the piston path, the pressure of the gas supplied to the device, the rotational velocity, the length of time that the pressured gas is supplied and, most importantly, the mass of the free piston, all are significant factors affecting the performance of the apparatus. A computer simulation of the aforedescribed device revealed that for a number of selected dimensions, pressures and weights, while high torque was produced during a period of the operating cycle no significant net torque was produced by the aforedescribed device whenever it was assumed that the apparatus was continuously rotating. These results would obviously seriously limit the utility of the aforedescribed apparatus.
The same type of computer simulation was also performed for a variety of other centrifugal piston expander configurations, such as those disclosed in the co-pending application of EDWIN WALTER DIBRELL, Ser. No. 436,412, filed Oct. 25, 1982 now U.S. Pat. No. 4,449,379 and assigned to the Assignee of the instant application. Thus, the cylinder configuration can range from a straight line or linear path of movement for the free piston to a curved path of movement terminating proximate to the axis of rotation, a spiral path, or even a helical-spiral path, all as disclosed in said co-pending application. The computer simulation of other types of configurations also indicated that for certain combinations of the aforementioned variables involved in the design of a particular expander, the resultant torque output could be best described as an oscillating torque operating on the rotating body mounting the centrifugal piston expander and, in some instances, being superimposed on a positive torque operating in a constant direction.